This year is Wallace Year, for it marks the centennial of the death of Alfred Russel Wallace. In 1857 he wrote to Charles Darwin, pre-empting his idea of natural selection, and Darwin, a true Victorian gent, suggested that they present a joint paper on the idea. Wallace, in turn, became his devotee, and is remembered mainly in that role.

In truth, he did far more. He started off life as a surveyor, and set out the street plan of Llandrindod Wells, in the Welsh borders. He then designed a council building in Neath. He travelled in South America, where his brother died and the ship carrying his specimens caught fire and sank.

In the midst of all this, Wallace founded the science of biogeography, the attempt to make sense of the distribution of animals and plants. In a map made in 1876 he defined six great regions of life; and in so doing predicted, without realising it, the greatest discovery of geology in the past century, the idea of continental drift.

In Indonesia, he discovered a discontinuity in the patterns of animal distribution. A line – later called Wallace’s Line – drawn across the archipelago, with the Philippines, Borneo, Java and Bali to its north and west; and Lombok, Sulawesi and New Guinea to the south and east – separated two biological worlds. One had ties to Asia, with its fruit-thrushes, weaver birds and tigers, and the other to Australia, with cockatoos, honeyeaters and kangaroos. In some places, just 15 miles of sea separated the two provinces.

Why was this? In Wallace’s day the oceans were full of hypothetical land bridges, now sunk, which were said to have linked, for example, Australia, Africa and South America, to explain how flightless birds had got to all three. Wallace, too, appealed to the imagined landscape of Lemuria, a continent sunk in the Pacific, to explain the connection between Indonesia and Madagascar.

In fact, the ancient history of the continents as they broke up is to blame. The country east of his line was part of one giant fragment, while those to the west were on another. No lost continent is required, just one that moves around.

The latest version of Wallace’s map is based on 20,000 vertebrates, from frogs to sparrows and mice. His six great realms have gone up to 11. Three – Australia, Madagascar, and South America – have a strong identity of their own. Panama and China are given an enhanced status, but the Arctic has lost some of its personality, for the American and Siberian sections, once seen as distinct, are in fact much the same. On the larger scale, the Southern Hemisphere is much more subdivided than the Northern, perhaps because its oceans are wider and it has been less plagued by ice ages.

Geography is about maps, history is about chaps, and in Wallace’s day, the geological and zoological record was mainly about gaps. Now, everything has changed. We have specimens and relics from all over the world, and molecular biology has given us a new geography under the skin. The family tree of the mammals has been built with DNA. At first sight, it makes little sense, for it ties elephants to sea cows and anteaters to armadillos. In fact, the molecular pedigree – like Wallace’s map – links mammalian evolution to the break-up of Pangaea, the ancient world continent. Elephants, hyraxes, sea cows and golden moles trace a common root in Africa. Another group – anteaters, tree sloths and armadillos – find their origin in what is now South America.

The northern breakaway continent of Laurasia was the birthplace of bats, whales, dogs, cats, hedgehogs and more, all of which were born on that now shattered landscape. Parts of Laurasia itself split up to form islands that later emerged as North America, Europe, Siberia and parts of China. Rodents, hares and rabbits, tree shrews and the primates – the group to which apes, monkeys, lemurs and humans belong – were all born on the island of Eurasia.

Wallace was interested in much more than geography. He wanted to nationalise the railways, worked out that the Martian “canals” could not, for physical reasons, contain water and as early as 1909 wrote a bitter attack on the use of “flying machines in war”. I once tried to film an interview outside his edifice in Neath, but was interrupted by a group of terrible old ladies who hung out of the windows of the old people’s home next door, and shouted out: “Film us, we’re old fossils, too!”

Wallace, too, is one of those – but his ideas, from train fares to drone attacks to geology – have a very modern air. How many of the greats of today will be able to say the same a century from now?